1. Technical Field
The present disclosure relates generally to devices used for detecting the presence of obscured features behind opaque, solid surfaces, more specifically, devices used for locating beams and studs behind walls and joists beneath floors.
2. Background
The need to locate obscured features such as beams, studs, joists and other support elements behind walls and beneath floors is a common problem encountered during construction, repair and home improvement activities. Often a need exists to cut or drill into a supported surface with the aim of creating an opening in the surface while avoiding the underlying support elements. In these instances, it is desirable to know where the support elements are positioned before beginning so as to avoid cutting or drilling into them. On other occasions, one may desire to anchor a heavy object to the obscured support element. In these cases, it is often desirable to install a fastener through the surface in alignment with the underlying support element. However, once the wall, floor or surface is in place, the location of the support element is not visually detectable.
A variety of rudimentary techniques have been employed with limited success to address this problem in the past. These have included driving small pilot nails through the surface until a support element is detected and then covering over holes in the surface that did not reveal the location of the stud or support. A less destructive technique comprises tapping on the surface in question with the aim of detecting audible changes in the sound which emanates from the surface when there is a support element beneath or behind the area being tapped. This technique is not very effective, however, because the accuracy of the results depends greatly on the judgment and skill of the person searching for the support, and because the sound emitted by the tapping is heavily influenced by the type and density of the surface being examined.
Magnetic detectors have also been employed to find obscured support elements with the detector relying on the presence of metallic fasteners, such as nails or screws, in the wall and support element to trigger a response in the detector. However, since metallic fasteners are spaced at discreet locations along the length of a support, a magnetic detector may pass over a length of the support where no fasteners are located, thereby failing to detect the presence of the obscured support element.
Capacitive displacement sensors have also been employed to detect obscured features behind opaque surfaces. These detectors sense changes in capacitance on the examined surface that result from the presence of features positioned behind, beneath or within the surface. These changes in capacitance are detectable through a variety of surfaces such as wood, sheetrock, plaster, gypsum and do not rely on the presence of metal fasteners in the surface or obscured feature for activation of the sensor.
However, conventional capacitive sensors suffer from a number of shortcomings. Conventional detectors typically have a flat detecting surface and don't provide a mechanism to allow the position of sensor plates to accommodate the mild surface curvature that is common to many architectural surfaces. Many architectural surfaces, such as walls and floors, may appear flat upon casual observation. Nevertheless, they often have at least a mild degree of curvature. When a conventional, flat detector is placed on a curved surface, air gaps can emerge between the sensor plates and the detected surface. The readings of the detected surface can differ depending on whether or not an air gap is present. Consequently, air gap inconsistencies can make it more difficult to ascertain the depth and position of hidden features. The signals detected become less consistent and readings may be less reliable. If the surface has too much curvature, it may be difficult, or impossible, to detect hidden features. The problem with air gaps affects conventional capacitive sensing detectors, and may be more significant in larger detectors with more sensor plates and larger sensor plates.